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2.3 Probability

2.3 Probability

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Question 31

The Venn diagram shows the probabilities associated with three events DDD, E E\,E and FFF, representing users of three social media apps. The probability of using only D D\,D is 0.1, only E E\,E is 0.35, and only F F\,F is 0.2. The intersection D∩E D \cap E\,D∩E is q q\,q and E∩F E \cap F\,E∩F is ppp. Events D D\,D and F F\,F have no common outcomes. The probability of using none of the apps is rrr.

Venn diagram of events D, E and F, with D and F disjoint and E overlapping both, showing probabilities 0.1, q, 0.35, p, 0.2 and r.

a.

Write down the two events that are mutually exclusive.

[1]
b.

Given that P(E∣F)=0.2P(E | F) = 0.2P(E∣F)=0.2, find the value of ppp.

[2]
c.

Given also that D D\,D and E E\,E are independent, find the values of q q\,q and rrr.

[4]
Markscheme

2.3 Probability Questions

  1. A Level
  2. /Maths
  3. /2.3 Probability

200 exam-style questions on OCR A Level Maths 2.3 Probability, covering 2.3.1 Mutually exclusive and independent events, 2.3.2 Diagrams to assist probability calculations, 2.3.3 Conditional probability (A-level only), 2.3.4 Conditional probability from first principles (A-level only), and 2.3.5 Modelling with probability. Each one has a worked solution and a mark scheme showing where the marks go.

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